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MG Midget and Sprite Technical - bleed problem

Hi I have a 1974 midget I finish the complete restoration and everything is new brake hose pump etc

I bleed the brake a lot of time I begin by the rear brakes and I finish by the front and the pedal is perfect but the day after no more brake

I need held

thanks a lot


D.D. vmax207

You have an air leak, unless all your fluid is dripping onto that nice clean garage floor.
Lawrence Slater

Hi DD,

Now, isn't there something about the piston arrangement in the brake master cylinder that can be assembled wrongly, allowing the pressure to leak back past the seals without actually loosing any fluid from the system?

Sorry I cannot remember the details on this, but someone will recognise what I am referring to.

But that apart, that paint finish on your car is just superb. From your e-mail address I presume you are "in the trade" for car painting?
Guy

Yes. Nice paint, in fact nice everything. The hood fits superbly.

Bernie.
b higginson

We had a real problem with one of the Midgets once. No air in or enterning the system, but still hardly any pedal - a real mystery.

It proved to be the new seals being too grippy on the also new caliper pistons, not allowing them to move through fully and self adjust, but rather acting as a spring and retracting them half a mm or even a bit more when the pedal was released.

Dismantled, cleaned, put a different lubricant on them and that solved the problem.
Paul Walbran

I've had similar problems to Paul with the earlier duel cylinders. Strip it, check it and re-lube.

Also use the correct DOT 3 fluid. DOT 4 or 5 are designed for a different profile seal and can effect the performance of earlier type seals.

Another thing to consider is if you have a duel circuit system with that little shuttle valve on the inner wing... bleeding those can be a trauma..

Good luck,

Mark.
M T Boldry

Not sure that's right MT.

Dot 3/4 are essentially the same mix, and Dot5 is Silicone.

Dot4 supercedes Dot3 with a higher boiling point. So Dot 4 should be the way to go I think. Or the newer DOT 5.1 glycol fluids, since they are compatible with DOT 3 and 4.



Lawrence Slater

if you've replaced the flexi hoses... make sure they are sealing to their connections... its a flat connection (no flare) so it needs to be torqued to FT... a copper washer can help here too.
C L Carter

This thread was discussed between 01/12/2011 and 07/12/2011

MG Midget and Sprite Technical index

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